IP Multimedia (IPMM) services provide a dynamic combination of voice, video, messaging, data, etc. within the same session. By growing the numbers of basic applications and the media which it is possible to combine, the number of services offered to the end users will grow, and the inter-personal communication experience will be enriched. This will lead to a new generation of personalised, rich multimedia communication services, including so-called “combinational IP Multimedia” services which are considered in more detail below.
IP Multimedia Subsystem (IMS) is the technology defined (in TS 32.225, Release 5) by the Third Generation Partnership Project (3GPP) to provide IP Multimedia services over 3G mobile communication networks. IMS provides key features to enrich the end-user person-to-person communication experience through the integration and interaction of services. IMS allows new rich person-to-person (client-to-client) as well as person-to-content (client-to-server) communications over an IP-based network. The IMS makes use of the Session Initiation Protocol (SIP) and Service Delivery Protocol (SDP) to set up and control calls or sessions between user terminals (or user terminals and web servers). IMS sits on top of an access network which would typically be a General Packet Radio Service (GPRS) network but which might use some alternative technology, e.g. WiFi. FIG. 1 illustrates schematically how the IMS fits into the mobile network architecture in the case of a GPRS access network. IMS will also form part of 3GPP Universal Mobile Telecommunications System (UMTS) network architectures.
An example of a combinational IP Multimedia service is a multimedia service that includes and combines both a Circuit Switched media (such as voice) and a Packet Switched media over the IP Multimedia domain (such as pictures, video, presence, instant messages, etc.). A service referred to here as “WeShare ” combines the full IP Multimedia Subsystem (IMS) benefits of a multimedia service with CS voice. The service enables a user, during a Circuit Switched (CS) voice conversation with another user, to take a picture, a video or audio clip, etc. and to share this content with other users in (near) real time using the Packet Switched (PS) domain. Either party in the conversation may initiate transmission of content to the other party.
In order to convey the PS data, e.g. a picture, a Packet Data Protocol (PDP) context needs to be setup and a PS bearer (Radio Access Bearer (RAB)) established. The former is a logical association between the user terminal and the network, running across the GPRS network, which defines aspects such as routing, quality of service, etc. The latter is the physical channel resources which will actually transport the picture data. The current assumption for combinational services is that the PDP context will be setup when the CS (speech) call is established and is maintained throughout the CS call. The PS bearer needed to transmit the picture is only setup when the user wants to send a picture, and is released some time after the picture has been transmitted.